Plasma health determination in semiconductor substrate processing reactors

ABSTRACT

Methods of monitoring a plasma while processing a semiconductor substrate are described. In embodiments, the methods include determining the difference in power between the power delivered from the plasma power supply and the power received by the plasma in a substrate processing chamber. The power received may be determined using a V/I sensor positioned after the matching circuit. The power reflected or the power lost is the difference between the delivered power and the received power. The process may be terminated by removing the delivered power if the reflected power is above a setpoint. The VRF may further be fourier transformed into frequency space and compared to the stored fourier transform of a healthy plasma process. Missing frequencies from the VRF fourier transform may independently or further indicate an out-of-tune plasma process and the process may be terminated.

TECHNICAL FIELD

The present technology relates to semiconductor systems, processes, andequipment.

More specifically, the present technology relates to terminatingout-of-tune plasma processes early.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers, or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess that etches one material faster than another facilitating, forexample, a pattern transfer process. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits, and processes, etch processes have been developedwith a selectivity towards a variety of materials.

Etch processes may be referred to as wet or dry based on the phase ofthe etchants used in the process. Wet processes have difficultypenetrating some constrained trenches and also may sometimes deformpatterned features. Dry etches are preferred when suitable chemistriesare available and known. Dry etch chemistries incorporating remoteplasma excitation and ion filtering have broadened the etchselectivities available to semiconductor manufacturers. The broadeningappeal of low intensity plasmas has created a need to determine thehealth of remote and local plasmas and take corrective action.

SUMMARY

Methods of monitoring a plasma while processing a semiconductorsubstrate are described. In embodiments, the methods include determiningthe difference in power between the power delivered from the plasmapower supply and the power received by the plasma in a substrateprocessing chamber. The power received may be determined by a V/I sensorpositioned after the matching circuit and calculated byV_(RF)×I_(RF)×cos(Φ_(RF)). The power reflected or the power lost is thedifference between the delivered power and the received power. The lostpower may be lost as heat in the matching circuit. The process may beterminated by removing the delivered power if the reflected power isgreater than, e.g., 20% of the delivered power. The methods may be usedto terminate etch processes or deposition processes in embodiments. Themethods may be used to terminate processes having a local (direct orbias) plasma or a remote plasma. The V_(RF) may further be fouriertransformed into frequency space and compared to the stored fouriertransform of a healthy plasma process. Missing frequencies from theV_(RF) fourier transform may independently or further indicate anout-of-tune plasma process and the process may be terminated.

Aspects of disclosed embodiments include methods of forming a plasma.The methods include flowing a precursor into a region. The region iswithin a substrate processing chamber. The methods further includeturning on an RF power from an RF power supply disposed outside theregion. The methods further include analyzing the RF power in a V/Iprobe disposed between the RF power supply and the region. Analyzing theRF power in the V/I probe determines a time-based voltage spectrum,voltage amplitude, a current amplitude and a voltage-current phasedifference, The methods further include delivering the RF power toregion to excite an RF plasma within the region from the precursor. Themethods further include calculating a power delivered to the RF plasmaby multiplying the voltage amplitude by the current amplitude andfurther by a cosine of the voltage-current phase difference. The methodsfurther include calculating a power difference between the RF power andthe power delivered to the RF plasma and then calculating adimensionless ratio of the power difference to the RF power. The methodsfurther include calculating a candidate frequency-based voltage spectrumfrom the time-based voltage spectrum. The methods further includecomparing a frequency-based voltage spectrum difference between thecandidate frequency-based voltage spectrum and a known-goodfrequency-based voltage spectrum to determine whether features presentin either frequency-based spectrum are missing from the otherfrequency-based spectrum. The methods further include terminating the RFpower from the RF power supply if the dimensionless ratio is greaterthan 0.21 or the features present in either spectrum are missing fromthe other spectrum. Features present in the candidate frequency-basedvoltage spectrum may be missing from the known-good frequency-basedvoltage spectrum or features present in the known-good frequency-basedvoltage spectrum may be missing from the candidate frequency-basedvoltage spectrum in embodiments.

The precursor may include fluorine. The RF plasma may be between 1 wattand 1,000 watts. A pressure in the region may be between 70 mTorr and 50Torr. The region may be a substrate processing region housing asubstrate. The region may be a remote plasma region separated from asubstrate processing region housing a semiconductor substrate and theremote plasma region may be separated from the substrate processingregion by a showerhead. The substrate processing region may beplasma-free during excitation of the RF plasma in the remote plasmaregion. An RF frequency of the RF power may be less than 200 kHz,between 10 MHz and 15 MHz or greater than 1 GHz during excitation of theRF plasma. Terminating the RF power from the RF power supply may includeapplying no RF power to the region before processing a substrate orbefore completely processing a substrate with the RF plasma.

Aspects of disclosed embodiments include methods of forming a localplasma. The methods include flowing a precursor into a substrateprocessing region housing a semiconductor substrate. The substrateprocessing region is within a substrate processing chamber. The methodsinclude turning on a local RF power from an RF power supply outside thesubstrate processing chamber. The methods further include analyzing thelocal RF power in a V/I probe configured between the RF power supply andthe substrate pedestal. Analyzing the local RF power in the V/I probedetermines a voltage amplitude, a current amplitude and avoltage-current phase difference. The methods further include deliveringthe local RF power to the substrate processing region to excite a localRF plasma within the substrate processing region from the precursor. Themethods further include calculating a power delivered to the local RFplasma by multiplying the voltage amplitude by the current amplitude andfurther by a cosine of the voltage-current phase difference. The methodsfurther include calculating a power difference between the local RFpower and the power delivered to the local RF plasma and thencalculating a dimensionless ratio of the power difference to the RFpower. The methods further include terminating the local RF power fromthe RF power supply if the dimensionless ratio is greater than 0.30.

An electron temperature within the substrate processing region may beless than 0.5 eV during excitation of the local RF plasma. The voltageamplitude and the current amplitude may be RMS values.

Aspects of disclosed embodiments include methods of forming a plasma.The methods include flowing a precursor into a substrate processingregion. The substrate processing region is within a substrate processingchamber. The methods further include turning on a bias RF power from anRF power supply disposed outside the substrate processing region. Themethods further include acquiring a time-based voltage spectrum of thebias RF power. The methods further include delivering the bias RF powerto the substrate processing region to excite a bias RF plasma within thesubstrate processing region from the precursor. The methods furtherinclude calculating a candidate frequency-based voltage spectrum fromthe time-based voltage spectrum. The methods further include comparing afrequency-based voltage spectrum difference between the candidatefrequency-based voltage spectrum and a known-good frequency-basedvoltage spectrum. The methods further include terminating the bias RFpower from the RF power supply if features present in eitherfrequency-based spectrum are missing from the other frequency-basedspectrum.

The frequency-based voltage spectrum difference may include at least onepeak at a frequency which is an integral multiple of a primary frequencyof the remote RF power. The remote RF plasma may becapacitively-coupled.

Such technology may provide numerous benefits over conventional systemsand techniques. For example, the measurements described herein may beused to determine the health of plasma processes whose reflected powermay be between 10% and 90% of the supplied power. Conventionaltechniques are constrained to reflected powers between 20% and 80% as aresult of the reliance of matching capacitor values in the matchingcircuit. These and other embodiments, along with many of theiradvantages and features, are described in more detail in conjunctionwith the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedtechnology may be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 shows a top plan view of an exemplary processing system accordingto the present technology.

FIG. 2 shows a schematic cross-sectional view of an exemplary processingchamber according to the present technology.

FIG. 3 shows a schematic of an exemplary plasma power supply matchingcircuit according to the present technology.

FIG. 4 shows selected operations in a method of forming a plasma in asubstrate processing chamber according to the present technology.

FIG. 5 is a chart showing a reflected power spectrum according toembodiments of the present technology.

FIG. 6 shows selected operations in a method of forming a plasma in asubstrate processing chamber according to the present technology.

FIG. 7A is a chart showing a voltage spectrum in the time domainaccording to the present technology.

FIG. 7B is a chart showing a voltage spectrum in the frequency domainaccording to the present technology.

Several of the figures are included as schematics. It is to beunderstood that the figures are for illustrative purposes, and are notto be considered of scale unless specifically stated to be of scale.Additionally, as schematics, the figures are provided to aidcomprehension and may not include all aspects or information compared torealistic representations, and may include additional or exaggeratedmaterial for illustrative purposes.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a letter thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the letter.

DETAILED DESCRIPTION

Methods of monitoring a plasma while processing a semiconductorsubstrate are described. In embodiments, the methods include determiningthe difference in power between the power delivered from the plasmapower supply and the power received by the plasma in a substrateprocessing chamber. The power received may be determined by a V/I sensorpositioned after the matching circuit and calculated byV_(RF)×I_(RF)×cos(Φ_(RF)). The power reflected or the power lost is thedifference between the delivered power and the received power. The lostpower may be lost as heat in the matching circuit. The process may beterminated by removing the delivered power if the reflected power isgreater than, e.g., 20% of the delivered power. The methods may be usedto terminate etch processes or deposition processes in embodiments. Themethods may be used to terminate processes having a local (direct, bias)plasma or a remote plasma. The V_(RF) may further be fourier transformedinto frequency space and compared to the stored fourier transform of ahealthy plasma process. Missing frequencies from the V_(RF) fouriertransform may independently or further indicate an out-of-tune plasmaprocess and the process may be terminated.

During substrate processing to deposit, etch, or treat a patternedsubstrate, it may be beneficial to have a plasma in a substrateprocessing chamber. The plasma may be a bias plasma (a local plasma)local to a substrate processing region in embodiments. The plasma may bea remote plasma in a remote plasma region separated from the substrateprocessing region by a showerhead according to embodiments. However,applying an RF plasma power from either a bias plasma power supply or aremote plasma power supply does not guarantee the formation of a plasmain the appropriate region. The formation of a healthy plasma depends onthe initial conditions in the region as well as transient phenomenonwhich occur in the region as the RF plasma power is initially applied.Benefits of the methods described herein include terminating substrateprocessing soon after a problem with the plasma is detected. Benefitsinclude preventing or reducing damage to a patterned substrate or simplysaving time which would have been lost on an out-of-tune plasma process.Details of the described methods will be presented following adescription of exemplary hardware.

FIG. 1 shows a top plan view of one embodiment of a substrate processingsystem 1001 of deposition, etching, baking, and curing chambersaccording to disclosed embodiments. In the figure, a pair of frontopening unified pods (FOUPs) 1002 supply substrates of a variety ofsizes that are received by robotic arms 1004 and placed into a lowpressure holding area 1006 before being placed into one of the substrateprocessing chambers 1008 a-f, positioned in tandem sections 1009 a-c. Asecond robotic arm 1010 may be used to transport the substrate wafersfrom the holding area 1006 to the substrate processing chambers 1008 a-fand back. Each substrate processing chamber 1008 a-f, can be outfittedto perform a number of substrate processing operations including theetch processes described herein in addition to cyclical layer deposition(CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD),physical vapor deposition (PVD), epitaxial silicon growth, etch,pre-clean, degas, orientation, and other substrate processes.

The substrate processing chambers 1008 a-f may include one or moresystem components for depositing, annealing, curing and/or etchingmaterial films on the substrate wafer. In one configuration, two pairsof the processing chamber, e.g., 1008 c-d and 1008 e-f, may be used todeposit dielectric material on the substrate, and the third pair ofprocessing chambers, e.g., 1008 a-b, may be used to etch the depositeddielectric. In another configuration, all three pairs of chambers, e.g.,1008 a-f, may be configured to etch a material on the substrate. Any oneor more of the processes described below may be carried out inchamber(s) separated from the fabrication system shown in differentembodiments. It will be appreciated that additional configurations ofdeposition, etching, annealing, and curing chambers for dielectric filmsare contemplated by system 1001. Many chambers may be utilized in theprocessing system 1001, and may be included as tandem chambers, whichmay include two similar chambers sharing precursor, environmental, orcontrol features.

FIG. 2 shows a schematic cross-sectional view of an exemplary substrateprocessing chamber. The schematic of the substrate processing chamber2001 serves to introduce the remote and local power supplies but alsoprovide context for alternative configurations and details provided insubsequent descriptions. Later drawings will provide less detailcompared to FIG. 2 but only for the sake of brevity. Any combination offeatures found in FIG. 2 may be present in any or all subsequentembodiments. The substrate processing chamber 2001 has a remote plasmaregion 2015 and a substrate processing region 2033 inside. The remoteplasma region 2015 is partitioned from the substrate processing region2033 by an ion suppressor 2023 and a showerhead 2025.

A top plate 2017, ion suppressor 2023, showerhead 2025, and a substratesupport 2065 (also known as a pedestal), having a substrate 2055disposed thereon, are shown and may each be included according to allembodiments described herein. The pedestal 2065 may have a heat exchangechannel through which a heat exchange fluid flows to control thetemperature of the substrate 2055. This configuration may allow thesubstrate 2055 temperature to be cooled or heated to maintain relativelylow temperatures, such as between −20° C. to 200° C. The pedestal 2065may also be resistively heated to relatively high temperatures, such asbetween 100° C. and 1100° C., using an embedded heater element.

The etchant precursors flow from the etchant supply system 2010 throughthe holes in the top plate 2017 into the remote plasma region 2015. Thestructural features may include the selection of dimensions andcross-sectional geometries of the apertures in the top plate 2017 todeactivate back-streaming plasma in cases where a plasma is generated inremote plasma region 2015. The top plate 2017, or a conductive topportion of the substrate processing chamber 2001, and the showerhead2025 are shown with an intervening insulating ring 2020, which allows anAC potential to be applied to the top plate 2017 relative to theshowerhead 2025 and/or the ion suppressor 2023. The insulating ring 2020may be positioned between the top plate 2017 and the showerhead 2025and/or the ion suppressor 2023 enabling a capacitively-coupled plasma(CCP) to be formed in the remote plasma region 2015. The remote plasmaregion 2015 houses the remote plasma.

The plurality of holes in the ion suppressor 2023 may be configured tocontrol the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 2023. For example,the aspect ratio of the holes, or the hole diameter to length, and/orthe geometry of the holes may be selected so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 2023 is reduced. The holes in the ion suppressor 2023 mayinclude a tapered portion that faces the remote plasma region 2015, anda cylindrical portion that faces the showerhead 2025. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to and through the showerhead 2025. An adjustableelectrical bias may also be applied to the ion suppressor 2023 as anadditional means to control the flow of ionic species through thesuppressor. The ion suppressor 2023 may function to reduce or eliminatethe amount of ionically charged species traveling from the plasmageneration region to the substrate. Uncharged neutral and radicalspecies may still pass through the openings in the ion suppressor toreact with the substrate.

Remote plasma power can be of a variety of frequencies or a combinationof multiple frequencies. The remote plasma may be provided by remote RFpower delivered from the remote plasma power supply 2068 to the topplate 2017 relative to the ion suppressor 2023, relative to theshowerhead 2025, or relative to both the ion suppressor 2023 and theshowerhead 2025 (as shown). The remote RF power may be between 10 wattsand 10,000 watts, between 10 watts and 5,000 watts, preferably between25 watts and 2000 watts or more preferably between 50 watts and 1500watts to increase the longevity of chamber components. The remote RFfrequency applied in the exemplary processing system to the remoteplasma region may be low RF frequencies less than 200 kHz, higher RFfrequencies between 10 MHz and 15 MHz, or microwave frequencies greaterthan 1 GHz in embodiments. The plasma power may be capacitively-coupled(CCP) or inductively-coupled (ICP) into the remote plasma region.

Plasma effluents derived from the etchant precursors in the remoteplasma region 2015 may travel through apertures in the ion suppressor2023, and/or the showerhead 2025 and into the substrate processingregion 2033 through through-holes or the first fluid channels 2019 ofthe showerhead in embodiments. Little or no plasma may be present insubstrate processing region 2033 during the remote plasma etch process.The plasma effluents react with the substrate to etch material from thesubstrate.

The showerhead 2025 may be a dual channel showerhead (DCSH). The dualchannel showerhead 2025 may provide for etching processes that allow forseparation of etchants outside of the substrate processing region 2033to provide limited interaction with chamber components and each otherprior to being delivered into the substrate processing region 2033. Theshowerhead 2025 may comprise an upper plate 2014 and a lower plate 2016.The plates may be coupled with one another to define a volume 2018between the plates. The plate configuration may provide the first fluidchannels 2019 through the upper and lower plates, and the second fluidchannels 2021 through the lower plate 2016. The formed channels may beconfigured to provide fluid access from the volume 2018 through thelower plate 2016 via the second fluid channels 2021 alone, and the firstfluid channels 2019 may be fluidly isolated from the volume 2018 betweenthe plates and the second fluid channels 2021. The volume 2018 may befluidly accessible through a side of the showerhead 2025 and used tosupply an unexcited precursor in embodiments.

A bias plasma power may be present in the substrate processing region inembodiments. The bias plasma may be used alone or to further exciteplasma effluents already excited in the remote plasma. The bias plasmarefers to a local plasma located above the substrate and inside thesubstrate processing region. The term bias plasma is used since theplasma effluents may be ionized and/or accelerated towards the substrateto beneficially accelerate or provide incoming alignment to some etchprocesses. In embodiments, a bias plasma may be present when no remoteplasma is used. The bias plasma may be formed by applying bias plasmapower from a bias plasma power supply 2070 to the substrate2055/pedestal 2065 relative to the ion suppressor 2023, relative to theshowerhead 2025, or relative to both the ion suppressor 2023 and theshowerhead 2025 (as shown). The bias RF plasma power may be lower thanthe remote RF power. The bias RF plasma power may be below 20%, below15%, below 10% or below 5% of the remote RF plasma power. The bias RFplasma power may be between 1 watt and 1,000 watts, between 1 watt and500 watts, or between 2 watts and 100 watts in embodiments. The bias RFplasma frequency applied in the exemplary processing system to thesubstrate processing region may be low RF plasma frequencies less than200 kHz, higher RF plasma frequencies between 10 MHz and 15 MHz, ormicrowave frequencies greater than 1 GHz in embodiments. The plasmapower may be capacitively-coupled (CCP) or inductively-coupled (ICP)into the substrate plasma region.

A waste of electrical energy may be reduced, avoided or minimized, inembodiments, by including a remote plasma power matching circuit 2069between the remote plasma power supply 2068 and the top plate 2017. Abias plasma power matching circuit 2071 may be electrically disposedbetween the bias plasma power supply 2070 and the substrate 2055 and/orpedestal 2065, according to embodiments, to reduce, avoid or minimizethe power demanded by the bias plasma power supply 2070 to achieve atarget power in the substrate processing region 2033.

Substrate processing chamber 2001 may be used to deposit or etchmaterials or perform operations discussed in relation to the presenttechnology. Substrate processing chamber 2001 may be utilized with aplasma formed in either the remote plasma region 2015 or the substrateprocessing region 2033. In embodiments, a plasma may be in each of theremote plasma region 2015 and the substrate processing region 2033contemporaneously in the etching or deposition operations describedherein. Substrate processing chamber 2001 is included only as anexemplary chamber that may be utilized in conjunction with the presenttechnology. It is to be understood that operations of the presenttechnology may be performed in substrate processing chamber 2001 or anynumber of other chambers.

FIG. 3 shows a schematic of an exemplary plasma power supply matchingcircuit according to the present technology. The exemplary circuitapplies to a local (bias) plasma, however, the technologies describedherein may be applied to a remote plasma in embodiments. A bias plasmapower supply 3018 delivers RF power to a matching circuit 3029. Thematching circuit 3029 may include a first variable capacitor 3030, afixed inductor 3031 and a second variable capacitor 3032. A V/I probe3040 receives the output from the matching circuit 3029 and may be usedto measure voltage spectrum properties, current spectrum properties, aswell as any phase difference between the voltage spectrum and currentspectrum. The voltage output from the V/I probe 3040 is delivered to thesubstrate by way of a pedestal in the substrate processing chamber 3050.A computer control system 3045 is configured to output instructions toall the components listed and to receive data from the components inembodiments.

The matching circuit 3029 is used to adjust the impedance of theassembly outside bias plasma power supply 3018 to equal 50Ω, ifpossible, to “match” the internal output impedance of the bias plasmapower supply 3018. Conventionally, the substrate processing may beaborted if the matching circuit 3029 is unable to adjust the impedanceto 50Ω or when the variable capacitors end up at values which ouroutside a normal range. The methods described herein use alternativecriterion to determine whether processing should be aborted.

FIG. 4 shows selected operations in a method 4001 of processing apatterned substrate (e.g. etching using a remote and/or local plasma toexcite etchants) in the substrate processing chamber 2001 as previouslydescribed. The method 4001 may include one or more operations prior tothe initiation of the method, including front-end processing,deposition, etching, polishing, cleaning, or any other operations thatmay be performed prior to the described operations. A processedsubstrate, which may be a semiconductor wafer of any size, may be placedwithin the substrate processing chamber for the method 4001. Subsequentoperations to those discussed with respect to method 4001 may also beperformed in the same chamber or in different chambers as would bereadily appreciated by the skilled artisan.

The method 4001 may optionally include placing a patterned substrateinto a substrate processing region of a semiconductor processingchamber. The semiconductor substrate may include a plurality of exposedportions of various distinct materials. The method 4001 includes flowinga precursor (e.g. a fluorine-containing precursor) into a substrateprocessing region of a semiconductor processing chamber at operation4005. The method 4001 includes turning on the RF power to a bias plasmain the substrate processing region in operation 4010. The remote plasmaregion and the substrate processing region are both in the samesubstrate processing chamber but are separated by a porous barrier suchas a showerhead. In general, the precursor may be a deposition precursoror an etching precursor. The etching precursor may include a halogen(e.g. fluorine or chlorine).

The voltage and current waveforms are acquired in a V/I probe prior toapplication to the substrate pedestal in the substrate processingregion. The voltage is applied to the substrate pedestal relative to theshowerhead or to the showerhead relative to the substrate pedestal. Inthe case of a remote plasma (not shown), the voltage may be applied tothe top plate relative to the showerhead or to the showerhead relativeto the top plate. The power applied (P_(CAL)) to the local plasma (orremote plasma in embodiments) is calculated as V_(RMS) multiplied byI_(RMS) multiplied by the cosine of the angular shift in time-domainbetween the voltage and current waveforms. In operation 4015, P_(CAL) issubtracted from the power delivered (P_(DEL)) by the bias plasma powersupply to find the reflected power (P_(REF)). The absolute value of thereflected power is divided by the delivered power to determine thefraction of power reflected. The fraction of power reflected may bemultiplied by one hundred to determine the percentage of the power whichis reflected and percentages of reflected power are referred to herein.

A decision is made based on the percentage of reflected plasma power inoperation 4020. If the percentage of reflected power is below athreshold percentage, the patterned substrate is processed (e.g. etchedwith fluorine-containing plasma effluents) in operation 4025. The RFplasma power to the substrate processing region is turned off, inoperation 4030, after the patterned substrate is processed. However, theRF plasma power is turned off without processing the patterned substrate(or before completely processing the substrate) if the power differenceis greater than 30% (0.30 in dimensionless ratio) of the RF plasmapower. Generally speaking the threshold percentage may be 21%, may be24%, may be 27%, may be 30%, may be 33%, may be 36%, or may be 39%according to embodiments.

FIG. 5 is a chart showing reflected power spectra according toembodiments of the present technology. Two reflected power spectra areshown for an in-tune plasma process 5020 and an out-of-tune plasmaprocess 5010. The data for each spectra are shown as percentagescalculated as described previously. A line indicating an exemplarythreshold percentage 5030 is also shown at 30%. In embodiments, thepercentage is calculated at least every 0.1 seconds, at least every 0.2seconds, at least every 0.3 seconds, at least every 0.5 seconds, or atleast every 1 second. If any calculated percentage value in a reflectedpower is above the threshold percentage (30% in the example) then theplasma process is terminated and the RF power is turned off according toembodiments. The out-of-tune reflected power spectrum 5010 indicatesthat the process would begin terminating at about 5 seconds into theprocess as measured on the horizontal axis. The in-tune reflected powerspectrum 5020 stays below 30% and would not be terminated.

The processes described herein examine the health of a plasma in asubstrate processing chamber indirectly using hardware which has oftenalready been included in a substrate processing system. A benefit ofusing the processes described herein, therefore, includes a reduction inhardware complexity compared to some alternatives. Some conventionalmethods for determining the health of a plasma may include equipping asubstrate processing chamber with a viewport and an optical emissionspectrometer to more directly determine the presence of a healthyplasma. Installing and maintaining optical emission spectrometers wouldincrease the costs of the hardware and maintenance procedures. Thebenefits of the processes described herein include a reduction in costsfor a manufacturer. Reflected power percentages were measured under avariety of circumstances. During a healthy plasma, the steady state(following the transient peak) reflected power measured was about 20%.By comparison, a plasma ignition fault resulted in a steady statereflected power measurement of about 48%. The steady state reflectedpower was measured to be 66% during a high reflected power fault.

The pressure in the remote plasma region and/or in the substrateprocessing region may be selected to benefit the deposition or etchingprocess (operation 4025 in the previous example). The pressure withinthe remote plasma region may be below 50 Torr, below 40 Torr, below 20Torr, below 10 Torr, below 5 Torr, below 2 Torr, below 1 Torr, below 800mTorr, below 600 mTorr, or below 500 mTorr according to embodiments. Thepressure in the remote plasma region may be maintained above 70 mTorr,above 100 mTorr, above 200 mTorr, above 500 mTorr, above 1 Torr, above 2Torr, or above 5 Torr in embodiments. For local (bias) plasmas, thepressure within the substrate processing region may be below 50 Torr,below 40 Torr, below 20 Torr, below 10 Torr, below 5 Torr, below 2 Torr,below 1 Torr, below 800 mTorr, below 600 mTorr, or below 500 mTorraccording to embodiments. The pressure in the substrate processingregion may be maintained above 70 mTorr, above 100 mTorr, above 200mTorr, above 500 mTorr, above 1 Torr, above 2 Torr, or above 5 Torr inembodiments. Inert additives or diluents (e.g. nitrogen (N₂) or argon(Ar)) may be combined with a deposition or etching precursor accordingto embodiments. A benefit of the processes described herein includesdetermining the health of low pressure plasmas which may be moretemperamental.

The RF plasma power applied to either the remote plasma region or thesubstrate processing region may be between 1 watt and 1,000 watts,between 1 watt and 500 watts, or between 2 watts and 100 watts inembodiments. The RF plasma frequency applied to the remote plasma regionor the substrate processing region may be low RF plasma frequencies lessthan 200 kHz, higher RF plasma frequencies between 10 MHz and 15 MHz, ormicrowave frequencies greater than 1 GHz according to embodiments. TheRF plasma power may be capacitively-coupled (CCP) or inductively-coupled(ICP) into either or both the remote plasma region and/or the substrateprocessing region.

Substrate processing may be performed while the patterned substrate isbetween 25° C. and 600° C. In embodiments, the substrate temperature maybe greater than 25° C., greater than 50° C., greater than 100° C.,greater than 150° C., or greater than 200° C. during substrateprocessing. The substrate temperature may be less than 600° C., lessthan 550° C., less than 500° C., less than 450° C., less than 400° C.,or less than 350° C. during substrate processing according toembodiments.

FIG. 6 shows selected operations in a method 6001 of processing apatterned substrate in a substrate processing chamber. A patternedsubstrate is placed within a substrate processing region of asemiconductor processing chamber. The method 6001 includes flowing aprecursor (e.g. a fluorine-containing precursor) into a substrateprocessing region of a semiconductor processing chamber at operation6005. The method 6001 includes turning on the RF power to a bias plasmain the substrate processing region in operation 6010. The remote plasmaregion and the substrate processing region are both in the samesubstrate processing chamber but are separated by a porous barrier suchas a showerhead. In general, the precursor may be as describedpreviously.

The voltage and current waveforms are acquired in a V/I probe (operation6015) prior to application to the substrate pedestal in the substrateprocessing region. The voltage is applied to the substrate pedestalrelative to the showerhead or to the showerhead relative to thesubstrate pedestal. In the case of a remote plasma (not shown), thevoltage may be applied to the top plate relative to the showerhead or tothe showerhead relative to the top plate. FIG. 7A is a chart showing thevoltage spectrum in the time domain 7010 as acquired by a computercontrol system from the V/I probe. The voltage spectrum is fouriertransformed (operation 6016) into the frequency domain as shown in FIG.7B. FIG. 7B shows a primary frequency (the leftmost peak) and higherorder peaks at integer multiples of the base frequency. The basefrequency may be the lowest frequency repetition evident in FIG. 7A.

The fourier transform of the voltage spectrum 7020 may have missingfeatures or extra features compared to a stored result of a healthyplasma according to embodiments. In FIG. 7A, the dotted line representsa peak which is present for a healthy plasma but missing for a plasmawhich is out-of-tune. In operation 6020, the stored healthy plasmafourier transform is compared with the measured fourier transform of thevoltage spectrum under test. The fourth order peak is determined to bemissing from the fourier transform of the voltage spectrum 7020 and thesubstrate processing is terminated by turning off the RF plasma power inoperation 6030 according to embodiments. If there are no differencesbetween the healthy plasma fourier transform and the fourier transformof the voltage spectrum 7020 under test, the substrate processing(operation 6025) proceeds and the RF plasma power is turned off aftersubstrate processing in operation 6030.

All film properties and process parameters given for each exampleprovided herein apply to all other examples as well. The deposition oretching precursor may be flowed into the remote plasma region or thesubstrate processing region, as appropriate, at a flow rate between 10sccm and 4000 sccm, between 200 sccm and 3000 sccm, or between 500 sccmand 2000 sccm in embodiments.

When a remote plasma is used but a bias plasm is not, the substrateprocessing region may be described herein as “plasma-free” during theprocesses described herein. Any or all of the methods described hereinmay have a low electron temperature in the substrate processing regionduring the processes to ensure the beneficial chemical reactions deepwithin the porous film according to embodiments. The electrontemperature may be measured using a Langmuir probe in the substrateprocessing region. In embodiments, the electron temperature may be lessthan 0.5 eV, less than 0.45 eV, less than 0.4 eV, or less than 0.35 eV.“Plasma-free” does not necessarily mean the region is devoid of plasma.Ionized species and free electrons created within the plasma region maytravel through pores (apertures) in the partition (showerhead) atexceedingly small concentrations. The borders of the plasma in thechamber plasma region are hard to define and may encroach upon thesubstrate processing region through the apertures in the showerhead.Furthermore, a low intensity plasma may be created in the substrateprocessing region without eliminating desirable features of theprocesses described herein. All causes for a plasma having much lowerintensity ion density than the chamber plasma region during the creationof the excited plasma effluents do not deviate from the scope of“plasma-free” as used herein.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theembodiments. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent technology. Accordingly, the above description should not betaken as limiting the scope of the technology.

Where a range of values is provided, it is understood that eachintervening value, to the smallest fraction of the unit of the lowerlimit, unless the context clearly dictates otherwise, between the upperand lower limits of that range is also specifically disclosed. Anynarrower range between any stated values or unstated intervening valuesin a stated range and any other stated or intervening value in thatstated range is encompassed. The upper and lower limits of those smallerranges may independently be included or excluded in the range, and eachrange where either, neither, or both limits are included in the smallerranges is also encompassed within the technology, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a layer” includes aplurality of such layers, and reference to “the precursor” includesreference to one or more precursors and equivalents thereof known tothose skilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”,“include(s)”, and “including”, when used in this specification and inthe following claims, are intended to specify the presence of statedfeatures, integers, components, or operations, but they do not precludethe presence or addition of one or more other features, integers,components, operations, acts, or groups.

1. A method of forming a plasma, the method comprising: flowing a precursor into a region, wherein the region is within a substrate processing chamber; turning on an RF power from an RF power supply disposed outside the region; analyzing the RF power in a V/I probe disposed between the RF power supply and the region, wherein analyzing the RF power in the V/I probe determines a time-based voltage spectrum, voltage amplitude, a current amplitude and a voltage-current phase difference; delivering the RF power to region to excite an RF plasma within the region from the precursor; calculating a power delivered to the RF plasma by multiplying the voltage amplitude by the current amplitude and further by a cosine of the voltage-current phase difference; calculating a power difference between the RF power and the power delivered to the RF plasma and then calculating a dimensionless ratio of the power difference to the RF power; calculating a candidate frequency-based voltage spectrum from the time-based voltage spectrum; comparing a frequency-based voltage spectrum difference between the candidate frequency-based voltage spectrum and a known-good frequency-based voltage spectrum to determine whether features present in either frequency-based spectrum are missing from the other frequency-based spectrum; terminating the RF power from the RF power supply if the dimensionless ratio is greater than 0.21 or a feature present in either frequency-based spectrum is missing from the other frequency-based spectrum.
 2. The method of forming the plasma of claim 1 wherein the precursor comprises fluorine.
 3. The method of forming the plasma of claim 1 wherein the RF plasma is between 1 watt and 1,000 watts.
 4. The method of forming the plasma of claim 1 wherein a pressure in the region is between 70 mTorr and 50 Torr.
 5. The method of forming the plasma of claim 1 wherein the region is a substrate processing region housing a substrate.
 6. The method of forming the plasma of claim 1 wherein the region is a remote plasma region separated from a substrate processing region housing a semiconductor substrate and the remote plasma region is separated from the substrate processing region by a showerhead.
 7. The method of forming the plasma of claim 6 wherein the substrate processing region is plasma-free during excitation of the RF plasma in the remote plasma region.
 8. The method of forming the plasma of claim 6 wherein an electron temperature within the substrate processing region is less than 0.5 eV during excitation of the plasma.
 9. The method of forming the plasma of claim 1 wherein an RF frequency of the RF power is less than 200 kHz, between 10 MHz and 15 MHz or greater than 1 GHz during excitation of the RF plasma.
 10. The method of forming the plasma of claim 1 wherein terminating the RF power from the RF power supply comprises applying no RF power to the region before processing a substrate or before completely processing a substrate with the RF plasma.
 11. A method of forming a local plasma, the method comprising: flowing a precursor into a substrate processing region housing a semiconductor substrate, wherein the substrate processing region is within a substrate processing chamber; turning on a local RF power from an RF power supply disposed outside the substrate processing chamber; analyzing the local RF power in a V/I probe disposed between the RF power supply and the substrate processing region, wherein analyzing the local RF power in the V/I probe determines a voltage amplitude, a current amplitude and a voltage-current phase difference; delivering the local RF power to the substrate processing region to excite a local RF plasma within the substrate processing region from the precursor; calculating a power delivered to the local RF plasma by multiplying the voltage amplitude by the current amplitude and further by a cosine of the voltage-current phase difference; calculating a power difference between the local RF power and the power delivered to the local RF plasma and then calculating a dimensionless ratio of the power difference to the local RF power; terminating the local RF power from the RF power supply if the dimensionless ratio is greater than 0.30.
 12. The method of forming the local plasma of claim 11 wherein the voltage amplitude and the current amplitude are RMS values.
 13. A method of forming a plasma, the method comprising: flowing a precursor into a substrate processing region housing a semiconductor substrate, wherein the substrate processing region are within a substrate processing chamber; turning on a bias RF power from an RF power supply disposed outside the substrate processing region; acquiring a time-based voltage spectrum of the bias RF power; delivering the bias RF power to the substrate processing region to excite a bias RF plasma within the substrate processing region from the precursor; calculating a candidate frequency-based voltage spectrum from the time-based voltage spectrum; comparing a frequency-based voltage spectrum difference between the candidate frequency-based voltage spectrum and a known-good frequency-based voltage spectrum; terminating the bias RF power from the RF power supply if features present in either frequency-based spectrum are missing from the other frequency-based spectrum.
 14. The method of forming the plasma of claim 13 wherein the frequency-based voltage spectrum difference comprises at least one peak at a frequency which is an integral multiple of a primary frequency of the bias RF power.
 15. The method of forming the plasma of claim 13 wherein the bias RF plasma is capacitively-coupled. 